The present invention relates generally to inductive heating, and more particularly, to a transverse flux heating coil having a single loop conductive heating element for heating a continuous run of wire therethrough.
The concept of transverse flux induction heating is well known. Typically, such heaters are used to heat strips of thin metal and have two inductor elements, each containing induction coils are arranged in a spaced, parallel relation. The metal strip to be heated is positioned between the two elements and on energizing the coils, magnetic flux is generated from current passing through the two inductor elements and passes through the strip perpendicular to its flat surfaces. This causes induced currents to circulate in the plane of the metal strip material to be heated and thereby causes the temperature in the metal strip to rise. Uniform heating is achieved when the strip is moved at a given speed between the two elements. Transverse flux induction heating operates at relatively high electrical frequencies which are chosen based on the thickness and properties of the metal strip to provide more efficient heating. Transverse flux-type induction coils are commonly used to heat such thin metal strips. Typically, in this type of an arrangement, a plurality of coils are placed adjacent one or both sides of the strip to be heated, and the strip is heated as it is conveyed past the coils. However, these types of induction heaters use an inordinate number of components, are difficult to impedance match with the power supply, and are therefore generally more costly to manufacture.
Where the work piece is a continuous run of wire, the prior art induction heaters use a plurality of coils wrapped around a heating area in which the wire is run through. To create a heating area of sufficient length to heat a wire run adequately at high speeds, the coil is wound about the heating area a number of times until a sufficient length is achieved. The current flowing through these solenoid-type coils causes flux generation in all directions around each turn of the coil. That is, as current travels through the turns of the inductor, flux is generated along the current path in a direction according to the well known right-hand rule. Using multiple turns of a coil thereby causes flux generation outwardly about the entire circumference of each turn of the coil, which results in a majority of the flux generated being other than transverse to the work piece, which in turn greatly reduces the efficiency of such solenoid coils.
It would therefore be advantageous and desirable to create a more efficient induction heating coil in which an increased amount of flux is directed into the heating area, and it would be additionally advantageous to provide therewith a means for simultaneously cooling the conductors of the heating coil.